Turbine blades are the primary elements of wind turbines for converting wind energy into electrical energy. The blades have the cross-sectional profile of an airfoil such that, during operation, air flows over the blade producing a pressure difference between the sides. Consequently, a lift force, which is directed from a pressure side towards a suction side, acts on the blade. The lift force generates torque on the main rotor shaft, which is geared to a generator for producing electricity.
The turbine blades typically consist of an upper (suction side) shell member and a lower (pressure side) shell member that are bonded together at bond lines along the trailing and leading edges of the blade. The bond lines are generally formed by applying a suitable bonding paste or compound along the bond line between the shell members. In some instances, a bond cap may be applied along the leading edge as well, and a bond paste or filler is used to blend the cap with the shell members. Typical bonding or adhesive materials include epoxies, acrylics, polyesters, vinyl esters, and urethanes.
It is a conventional practice to apply one or more coatings to the external substrate surfaces of the blade, for example a coating of paint or gelcoat. These coatings serve to protect the underlying substrate, provide a low friction surface to flowing air over the blade, and smooth out surface irregularities. The coatings are applied to all external surfaces of the blade, including over the exposed bonding and blending materials.
Inspection of blades in the field has revealed premature failure of the coatings in the areas that overlie the exposed bonding and blending materials, particularly along the leading edge of the blades. This situation results in significant repair/maintenance costs and down time for the wind turbine.
Accordingly, the industry would benefit from an improved wind turbine blade construction that reduces the occurrence of premature coating failures, particularly along the leading edge of the turbine blade.